1. Field of the Invention
The present invention relates to a system and method for measuring the velocity of a part that is moving through a part feeder.
2. Description of Related Art
During an assembly of an apparatus, such as an automobile engine or transmission, many of the fasteners used in the assembly are installed, tightened, and torqued by automated assembly equipment. The assembly equipment is integrated into the assembly line and receives the fasteners from a part feeder system that can sort, orient and deliver the fasteners to the assembly equipment. In the part feeder system, the fasteners are oriented and placed in a plastic tube through which the part can move from a storage magazine through the part feeder to the automatic assembly equipment.
The part feeder system is a pneumatic delivery system. Air is supplied to the magazine end of the plastic tube to propel the fastener through the plastic tube to the assembly equipment. If the velocity of the fastener is too great, the fastener will be moving too quickly when it arrives at the assembly equipment. If the fastener arrives while moving too quickly the part may misalign in the assembly equipment. In addition, if the fastener is moving too quickly, it can be damaged. In contrast, if the fastener moves too slowly through the plastic tube, the fastener can jam or stall in the plastic tube. In addition, if the fastener is moving too slowly, it may not align properly should it reach the assembly equipment.
The velocity at which the fastener moves through the plastic tube is determined in part by such factors as the volume and pressure of the air supplied to the tube. The volume and pressure of the air supplied to the tube is adjustable by a manually adjustable regulator. During manual adjustments, best judgments and guesses are used to adjust the volume and pressure to optimize the fastener""s velocity through the delivery tube. The adjustments will be made by different people during different shifts. Because the fastener""s velocity is controlled indirectly using the regulator, there is no direct measure of the fastener velocity. The potential for improper adjustment or improper fastener velocity can be higher using indirect measurement compared to direct measurement.
The present invention provides an apparatus for determining a velocity of a part through a part feeder tube. The part feeder tube defines an axis. The apparatus includes first and second sensors spaced axially from each other by a predetermined distance (d). The first sensor sends a first signal in response to sensing the part and the second sensor sends a second, subsequent signal in response to sensing the part. The velocity of the part is based on the distance (d) and the first and second signals.
The present invention also provides a method of determining the velocity of a part through a part feeder tube. The method includes the step of sensing initially when the part is within a predetermined first location and sensing subsequently when the part is within a predetermined second location. The second location is spaced a known, predetermined distance from the first location. The method includes the step of determining the elapsed time between the initial sensing and the subsequent sensing, and determining the velocity of the part using the elapsed time and the distance.